title: Overexpression of USF increases TGF-beta1 protein levels, but G1 phase arrest was not induced in FRTL-5 cells.
abstract: Transforming growth factor-beta1 (TGF-beta1) is a potent inhibitor of cellular growth and proliferation by G1 phase arrest or apoptosis. We investigated the association of TGF-beta1 with the anti-proliferative effect of upstream stimulatory factor (USF) in Fischer rat thyroid cell line (FRTL-5) cells. [methyl-(3)H] thymidine uptake was measured after treatment of FRTL-5 cells with TGF-beta1 to identify its anti-proliferative effect. USF-1 and USF-2 proteins were in vitro translated, and an electrophoretic mobility shift assay was performed to identify the interaction between USF and the TGF-beta1 promoter. FRTL-5 cells were transfected with USF cDNA, and then the expression of TGF-beta1 was examined with Northern and Western blotting. The cell cycle-regulating proteins associated with TGF-beta1 were also measured. TGF-beta1 significantly inhibited [methyl-(3)H] thymidine uptake in FRTL-5 cells. Two specific binding sites for USF were found in the TGF-beta1 promoter: -1,846 approximately -1,841 (CACATG) and -621 approximately -616 (CATGTG). Overexpression of USF increased both the mRNA levels and protein levels of TGF-beta1. However, the expression of cyclin D1, CDK4, cyclin E, and CDK2, and the phosphorylation of retinoblastoma protein remained unchanged. Overexpression of USF in FRTL-5 cells increased the expression of TGF-beta10 through specific binding to TGF-beta1 promoter. However, the USF-induced expression of TGF-beta1 did not cause G1 arrest.
authors.affiliation: Department of Medicine, Samsung Medical Center, Jungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Keun-Sook
authors.initials: KS
authors.lastname: Kim
authors.forename: Hye Seung
authors.initials: HS
authors.lastname: Jung
authors.forename: Yun Jae
authors.initials: YJ
authors.lastname: Chung
authors.forename: Tae Sik
authors.initials: TS
authors.lastname: Jung
authors.forename: Hye Won
authors.initials: HW
authors.lastname: Jang
authors.forename: Myung-Shik
authors.initials: MS
authors.lastname: Lee
authors.forename: Kwang-Won
authors.initials: KW
authors.lastname: Kim
authors.forename: Jae Hoon
authors.initials: JH
authors.lastname: Chung
mesh_terms: D000818:Animals; D017209:Apoptosis; D001665:Binding Sites; D002453:Cell Cycle; D002460:Cell Line; D016193:G1 Phase; D005786:Gene Expression Regulation; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D051381:Rats; D013936:Thymidine / Q000737:chemistry; D014162:Transfection; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D051720:Upstream Stimulatory Factors / Q000378:metabolism*
chemical_list: D053773:Transforming Growth Factor beta1; D051720:Upstream Stimulatory Factors; C497182:Usf1 protein, rat; C497187:Usf2 protein, rat; D013936:Thymidine